For an up-link from a UE (User Equipment) to a base station, 3GPP (3rd Generation Partnership Project), which has developed and proposed the W-CDMA (Wideband-Code Division Multiple Access) standard, has defined a DPDCH (Dedicated Physical Data Channel) as a data transfer channel and a DPCCH (Dedicated Physical Control Channel) as a control data channel (see Non-patent Document 1).
Furthermore, 3GPP Release 6 has additionally defined HSUPA (High Speed Uplink Packet Access) as a method to achieve high-data-rate uplink transfer. As shown in FIG. 1, the HSUPA achieves high-speed data communication by code-multiplexing an E-DPDCH (Enhanced Dedicated Physical Data Channel) as a data transfer channel and an E-DPCCH (Enhanced Dedicated Physical Control Channel) as a control data channel for the E-DPDCH additionally on uplink channels of the related W-CDMA (see Non-patent Document 1). Although FIG. 1 is a diagram showing a configuration of an HSUPA transmission system according to an exemplary embodiment of the present invention, that configuration is basically the same as a system configuration in the related art except an E-TFC selection controller 106.
Furthermore, there has been defined to code-multiplex an HS-DPCCH (High Speed Dedicated Physical Control Channel) for HSDPA (High Speed Downlink Packet Access) additionally on an uplink channel of the related W-CDMA for transfer of data re-transmission information or the like.
In an uplink of the W-CDMA, there are functions including a TFC (Transport Format Combination) selection for determining an optimum transmission rate of a DCH (Dedicated Channel) that conforms to a radio wave environment or a maximum permissible transmission power and an E-TFC (Enhanced Transport Format Combination) selection for determining an optimum transmission rate of an E-DCH (Enhanced Dedicated Channel) (see Non-patent Document 2).
When the number of transmission channels code-multiplexed is increased as described above, a PAR (Peak to Average power Ratio), which is a ratio of a peak power and an average power of a transmission signal, is increased such that distortion is caused in a PA (Power Amplifier), resulting in degradation of an ACLR (Adjacent Channel Leakage power Ratio).
In order to improve this situation, it is necessary to calculate a correction value to a maximum transmission power to obtain a maximum permissible transmission power (a quantity of reduction from the Maximum transmission power). For this correction value, an MPR (Max Power Reduction) conforming to a PAR is defined (see Non-patent Document 3).
The number of uplink channels multiplexed has been small for UEs until the 3GPP Release 5 HSDPA. Thus, the 3GPP has defined the specification for reducing a maximum transmission power in a fixed manner according to an amplitude value (βd) of a DPDCH. Three fixed values are stored and used for a quantity of reduction from a maximum transmission power according to a combination of βd in a look-up table (see Non-patent Document 4). For a TFC selection, an optimum TFC has been selected by using those three quantities of reduction according to βd.
Meanwhile, the number of channels code-multiplexed has been increased in the 3GPP Release 6 HSUPA, so that the number of β-combinations that can be multiplexed has explosively been increased. If a look-up table is used to determine a quantity of reduction, it is difficult to perform simple case classification. Therefore, there has been defined to sample a transmission waveform at a downstream side of an FIR (Finite Impulse Response) filter 103 which has been subjected to diffusion and filtering with respect to a determined β-combination so as to calculate a CM (Cubic Metric) and then an MPR, rather than to refer to an MPR from a β-combination in advance as in Release 5 (see Non-patent Document 5). However, this process imposes a large load. Therefore, if this process were to be performed just before transmission, the circuit would be complicated and increased in scale.
Non-patent Document 1: 3GPP Release 6 TS25.211 (v6.7.0) 5.2
Non-patent Document 2: 3GPP Release 6 TS25.133 (v6.13.0) 6.4
Non-patent Document 3: 3GPP Release 6 TS25.133 (v6.13.0) 6.5
Non-patent Document 4: 3GPP Release 5 TS25.101 (v5.13.0) 6.2.2
Non-patent Document 5: 3GPP Release 6 TS25.101 (v6.11.0) 6.2.2
Non-patent Document 6: 3GPP Release 6 TS25.214 (v6.9.0) 5.1.2.6